Driving apparatus for sound films



- Dec. 4, 1934- F. EHRENHAFT DRIVING APPARATUS FOR SOUND FILMS FiledJah. 10, 1930' Patented Dec. 4, 1934 UNITED STATES PATENT OFFICE DRIVINGAPPARATUS FOR SOUND FILMS Application January 10,

6 Claims.

My invention relates to a driving apparatus for sound films. It is anobject of my invention to provide an apparatus of the kind referred towhich can be adapted to any existing pictureprojecting camera.

To this end, I design the driving apparatus as an independent unit bymounting its parts, including means for scanning the sound record on thefilm, a guiding cylinder for the film which is preferably entrainedfrictionally by the film, and an eddy current brake for steadying therotation of the guiding cylinder; on a casing which is adapted to befitted to any existing picturefilm projecting apparatus or camera.

It is another object of my invention to provide means for instantlyarresting the moving element of the driving apparatus. To this end, Iprovide an electromagnet which is controlled by the energizing currentof the driving apparatus, as a member of the eddy current brake, and abrake block associated with the disk of the brake, the disk being oflight metal such as aluminium, and the brake block being adapted to belifted off the disk by the excited electromagnet; in combination withmeans such as a spring for applying the brake block to the disk when theelectromagnet is de-energized. By these means, the apparatus is arrestedimmediately the circuit of the current is interrupted.

In a preferred embodiment of my invention I so arrange and design thedriving apparatus that a loop is formed in the film at the apparatus,and the film is steadied while moving in the loop. The apparatus is anindependent unit which may be fitted to existing instruments. The movingelement of the apparatus which will be referred to as the guidingcylinder is entrained by the film under friction only. The cylinder, orpart of it, is operatively connected With an eddy-current brake which inorder to eliminate separate starting means is made very light, and maybe a disk of aluminium rotating in a magnetic field. Mechanical meansare connected with the disk, and preferably combined with its magnets,for arresting the guiding cylinder immediately, the apparatus is shutdown. Where means such as friction rollers under spring pressure areprovided for holding the film engaged with the cylinder, means may beprovided for lifting the rollers immediately the apparatus is arrestedso that the film is not stressed by the cylinder which obviously has atendency to continue its rotation.

In the accompanying drawing an apparatus to which my improved appliancehas been adapt- 1930, Serial No. 419,911 Germany January 16, 1929 ed,and two types of combined eddy-current and mechanical brakes, areillustrated diagrammatically by way of example.

In the drawing Fig. 1 is a partly sectional elevation of the completeapparatus,

Fig. 2 is a section on the line 22 in Fig. 1,

Fig. 3 is an elevation of a brake in which the aluminium disk is seatedon the shaft of the cylinder, and

Fig. 4 is an elevation of a brake in which the cylinder is connectedwith the brake by a belt or the like.

Referring now to the drawing, and first to Figs. 1 and 2, 1 is a frameor table, 9 is the easing of the sound-rendering appliance, 2 is the endof the projecting lamp, with its picture frame 5 and its optical system4, 3 is a supply, and 17 is a winding reel for the film 12; 6, 14, and15 are fixed guiding rollers for the film, '7 and 16 are toothed feedingcylinders, the first cylinder having the Geneva cross; 8 are a pair ofsteadying rails at the top of the casing 9, 19 is a spring-pressedroller acting on the film, 10 is the guiding cylinder, with aphoto-electric cell 11 therein, 13, 13, are friction rollers for holdingthe film engaged with the guiding cylinder 10, 18 is anotherspring-pressed roller intermediate the fixed rollers 14 and 15, and 26is an illuminating appliance for the casing 9.

It will appear that the film is taken around the cylinder 10 in theshape of a loop. The spring-pressed rollers 19 and 18 serve forgenerating slack reaches in the film so that the stepby-step feedingmotion of the cylinders 7 and 16 is not transmitted to the loopencircling the guiding cylinder 10. The cylinder, therefore, beingentrained by friction only by the fihn 12, under the pressure of therollers 13, 13, rotates at a uniform rate.

It will further appear that the casing 9 of the appliance is arrangedintermediate the supply and winding reels 3 and 17 and therefore may bereadily inserted and removed without interfering with other parts of theapparatus.

Referring now particularly to Fig. 2, the guiding cylinder 10 iscombined with a stationary part 10a, on a bracket 10b, and the cell 11projects into the gap 20 between the parts. Preferably the diameter ofthe stationary part is smaller than that of the cylinder 10 so thatfriction on the edge of the fihn is eliminated.

I may also provide an undivided guiding cylinder with a glass tubeinserted at the gap 20.

' Light is projected onto the cell 11 and through its the film 12 from asource of light 2'7 in the casing of the illuminating appliance 26,condensed by a lens 28, and defiected by a prism 29. The rays areprojected onto the cell 11 through the tone records on the film 12.

Means for steadying the rotation of the cylinder 10 comprisea shaft 21,in ball bearings 23, 24, an aluminium plate 22 on the shaft, andpermanent magnets 25. Brakes of this types are old and known as eddycurrent brakes. They effect a magnetic braking action the effect ofwhich is in proportional to the number of revolutions per min. of theguiding cylinder 10.

Figs. 3 and 4 illustrate magneto-mechanical brakes combined with thesteadying appliance.

Referring first to Fig. 3, instead of a permanent magnet, or magnets, anelectromagnet 30;

is provided in the circuit of the motor for driving the apparatus, notshown. The electromagnet is provided with a pole shoe 31 on the otherside of the disk 22. 33 is double-armed lever which is fulcrumed at 34,35 is a friction pad or block at one end of the lever, and 36 is aspring which tends to hold the pad 35 engaged with the disk 22. 32 is anarmature at the opposite end of the lever which is attracted by the shoe31 while the electromagnet 30 is excited, and holds the pad 35 away fromthe disk 22.. When the motor of the apparatus is cut out, theelectromagnet is de-energized and releases the lever 33 so that thespring 36 applies the pad 35 to the disk 22 and arrests the cylinder 10immediately.

Referring now to Fig. 4, 37 is a rocking bracket which is fulcrumed at38 and at one end supports the shaft 39 of the cylinder 10 while itsother (and supports the shaft 21 of the disk 22. The disk and thecylinder are operatively connected by' pulleys or sprockets 42, 43 ontheir respective shafts, and a cable, belt, or chain 44. 45 is anelectromagnet similar to the electromagnet 30, Fig. 3, 46 is an armatureat the end of the bracket 37 which faces the electromagnet, and 41 is afixed brake block adapted to be engaged by the disk 22 when a spring 40is free to pull the bracket 37 to the left. The operation is similar tothat described with reference to Fig. 3.. When the electromagnet 45 isenergized the bracket 37 is attracted by its armature 46 and the disk 22is free to rotate with the. cylinder 10. When the circuit of the motoris cut out the electromagnet 45 allows the spring 40- to move the disk22 into engagement with the block 41, so that the disk 22 and thecylinder 10 are arrested.

As compared with revolving weights for steadying the rotation of thecylinder in the manner of a fly wheel, my steadying means comprising thedisk 22 and its magnet, or magnets, has the advantage that means forspeeding up the guiding cylinder when starting are not required. Bycombining the steadying means with an eddy current brake, as described,the guiding cylinder 10 is immediately arrested.

I claim:

1. In a driving apparatus for sound films adapted to smoothly drive asound film at its point of reproduction, a guiding cylinder fri tionallyengaging said film, frictional rollers pressing said film upon saidcylinder, an eddy current brake associated with said cylinder comprisinga pivoted lever supporting at one end thereof said cylinder, a lightmetallic disk rotatably mounted at the other end thereof, drivingconnections between said cylinder and said disk, an electro-magnetcontrolled by the energizing current of the driving apparatus associatedwith said disk and adapted to attract said pivoted lever, fixed brakingmeans, and resilient means connected to said lever adapted to force saiddisk into engagement with said braking means and to separate saidcylinder from said frictional rollers when said energizing current isdisconnected from the apparatus.

2. In a driving apparatus for sound films, a casing adapted to be fittedto a picture-film projecting apparatus, a pivoted lever mounted on saidcasing, means for scanning the sound rec- 0rd on the film, also mountedon said casing and including a guiding cylinder for said film which issupported at one end of said lever, a light metallic disk rotatablymounted at the other end thereof, driving connections between saidcylinder and said disk, an eddy current brake associated with said disk,an electromagnet controlled by the energizing current of the drivingapparatus forming part of said eddy current brake and adapted to attractsaid pivoted lever, fixed braking means, and resilient means connectedto said lever adapted to force said disk into engagement with saidbraking means and to separate said cylinder from said film When saidenergizing current is disconnected from the apparatus.

3. In a driving apparatus for sound films adapted to smoothly drive asound film at its point of reproduction, a guide cylinder frictionallyengaging said film, a pivoted lever supporting at one end thereof saidcylinder, a light metallic disk rotatably mounted at the other endthereof, driving connections between said cylinder and said disk, aneddy current brake asso ciated with said disk, an electromagnetcontrolled by the energizing current of the driving apparatus associatedwith said disk and adapted to attract said pivoted lever, fixed brakingmeans, and resilient means connected to said lever adapted to force saiddisk into engagement with said braking means and to separate saidcylinder from said film when said energizing current is disconnectedfrom the apparatus.

4. In a driving apparatus for sound films, a casing adapted to besupplementarily fitted to a picture-film projecting apparatus of anysuitable commercial type, means mounted on said casing for scanning thesound record on the film comprising a guiding cylinder for said film anda photo-electric cell within said guiding cylinder, an eddy currentbrake for steadying the rotation of said cylinder, an electromagnetcontrolled by the energizing current of the driving apparatus andforming part of said eddy current brake, and a mechanical brake forarresting said cylinder upon the de-energization of said electromagnet.

5. In a driving apparatus for sound films, a casing adapted to besupplementarily fitted to a picture-film projecting apparatus of anysuitable commercial type, means mounted on said casing for scanning thesound record on the film comprising a guiding cylinder for said film anda photo-electric cell within said guiding cylinder, an eddy currentbrake comprising a rotating disc and an electromagnet for steadying therotation of said guiding cylinder, said electromagnet being controlledby the energizing current of the driving motor of said drivingapparatus, mechanical braking means associated with said rotating disccomprising means for exerting a mechanical force of lesser degree andwithin said guiding cylinder, an eddy current brake for steadying therotation of said. cylinder comprising a disc mounted on said shaft, andbearings for said shaft between said disc and said cylinder, anelectromagnet controlled by the energizing current of the drivingapparatus and forming part of said eddy current brake, a mechanicalbrake for arresting said cylinder upon the de-energization of saidelectromagnet, and means for rendering inoperative said brake upon theenergization of said electromagnet.

FRANZ EHRENHAFT.

